Stanford Law School published its latest report on US securities fraud class action lawsuits today. The always-interesting research notes that the number of filings fell by 25% in 2009. “Plaintiffs simply ran out of financial firms to sue, and the rising stock market made it harder for plaintiffs to assert claims,” said Joseph Grundfest, director of Stanford’s Securities Class Action Clearinghouse.

For the second consecutive year, financial firms were the most popular targets for lawsuits, accounting for around half of filings made last year.

The researchers also explain the recent drop in filings as a result of lower market volatility. The number of filings tracks the VIX index reasonably closely, as sharp movements in share prices lead investors to think that mismanagement is to blame, particularly when those movements are of the downward variety.